syncronous serial

[herley bird]

we have a custom serial signal that has a clock and a data valid line
syncronizing the serial stream line.

How/Can this be done with lab view 6.1 or 7 and a normal rs232 9 pin serial
port.

[Oleg]

Hi,
you can use VISA Write/Read functions from "Functions->Instrument I/O->Serial" palette. If you right-click on them you will find the "Do I/O Synchronously/Asynchronously" options in pop-up menu. You can select the proper one.
Try this. May be it will help.

Good luck.

Oleg Chutko.

[Dennis_Knutson]

Sounds like you need to have hardware handshaking turned on. VISA Configure Serial Port has a flow control setting.

[Dennis_Knutson]

Synchronous/asynchronous data communication is different than synchronous/asynchronous VISA driver operation. See the posting here.

[herley bird]

Dennis
Your last email link was broken
it may help...

Maybe some more info from me might also help
I need to respond to a clock and data valid line, then i will know my serial
line read is valid, how would i know when these two signals are at a high or
low state.
[I can connect them to any pin]

In VB 6 there was a rts rtd handshaking thing...I wanted to follow this idea
in LV.
what can be done in lab view via handshaking lines?

Thanks for your always ernest efforts.



"Dennis Knutson" wrote in message
news:506500000005000000E6FC0000-1042324653000@exchange.ni.com...
> Sounds like you need to have hardware handshaking turned on. VISA
> Configure Serial Port has a flow control setting.

[Pepe]

me wrote:
> Dennis
> Your last email link was broken
> it may help...
>
> Maybe some more info from me might also help
> I need to respond to a clock and data valid line, then i will know my serial
> line read is valid, how would i know when these two signals are at a high or
> low state.
> [I can connect them to any pin]
>
> In VB 6 there was a rts rtd handshaking thing...I wanted to follow this idea
> in LV.
> what can be done in lab view via handshaking lines?
>


Get a reference to a serial port, then open it with visa open.
Then set a visa propery node to read "modem line settings".
This is how you read/set the state of the CTS RTS lines.
I don't know what the performance is like but given that
loops will be done in software....

[Chris_Rake]

If you are looking to generate a serial clock that coincides with the serial data using a standard RS232 com port, then you may be out of luck.

A standard 16550 UART does not generate a syncronouse clock, and one can not be created using the serial handshake lines unless you are transmitting at very slow (300 baud may be too fast) rates. This is because you would have to programatically set/clear the modem line for every bit time of data being sent.

You may be able to create a fake clock that runs at 1/2 the baudrate by continuously writting 0x55 (1 stop, no parity) from another port of the same UART (must use the same baud clock source - ie: COM2 if using COM1). However this may have gaps and would exist even if you weren't transmitting data.